The venerable Windows Help program is not supported in Windows Vista out of the box. Furthermore, developers are explicitly prohibited from distributing it with their applications. The viewer is now available via a seperate download.
According to KB 917607, the 32-bit version of Windows Help is no longer being supported.
Therefore, starting with the Microsoft Windows Vista and the Microsoft Windows Server Code Name "Longhorn" operating system releases, the Windows Help program will not ship as a component of Windows. Also, third-party programs that include .hlp files are prohibited from redistributing the Windows Help program together with their products. Users who want to view 32-bit .hlp files must download the program from the Microsoft Download Center, and then install it on their computers. The download for Windows Help is still in development and will be available in early 2007.
Oddly enough, the 16-bit version will continue to ship with Vista.
A search showed only one .HLP file on my computer. Surprisingly, it was included in the VC++ 8.0 samples file from the May 2006 Edition of MSDN Library.
InfoQ Asks: Are you still using or creating .HLP files?